Hot-pressing-oriented graphene in Si3N4 composites for enhanced electromagnetic wave absorption in X and Ku bands

In this study, the oriented graphene within graphene/Si 3 N 4 composites was successfully achieved by two-step hot-press sintering. Microstructure analysis revealed that the graphene sheets were well dispersed in the Si 3 N 4 matrix and oriented perpendicular to the applied stress. The composites exhibited effective electromagnetic wave (EMW) absorption capabilities and good mechanical properties . The effective absorption bandwidth (EAB) was 9.63 GHz, nearly covering the entire X and Ku bands (8.2–18 GHz), and the minimum reflect loss (RL) was −24.23 dB when the graphene content reached 7 wt% at a thickness of 2.02 mm. Meanwhile, the oriented graphene/Si 3 N 4 composites demonstrated a bending strength of 576.66 MPa and a fracture toughness of 8.40 MPa·m 1/2 . The EMW absorption in these composites should be primarily due to polarization relaxation loss and conductivity loss, and the toughening mechanism should involve the graphene pull-out, crack bridging, and crack deflection. The graphene/Si 3 N 4 composites have a promising application in structurally integrated functional materials . • The oriented graphene within graphene/Si 3 N 4 composites was successfully achieved by hot-pressing. • The graphene sheets in composites were perpendicular to the applied stress. • The composites exhibited an EAB of 9.63 GHz, nearly covering the X and Ku bands (8.2‐18 GHz), with an RLmin of ‐24.23 dB. • The composites demonstrated a bending strength of 576.66 MPa and a fracture toughness of 8.40 MPa·m 1/2 .